Considering that they're referencing a third-party server population history aggregator website, I wouldn't consider Cowen and Company's claims to Gamasutra to be official in any capacity. However, given the other news we've been hearing lately and the near-weekly free play sessions that BioWare Austin has been offering, it wouldn't surprise me at all if a drop of 450,000 subscribers is that far off:

Cowen's Doug Creutz estimates that subscriber numbers for the game peaked at 1.7 million in February, and that by the end of the current fiscal year in March 2013, the game will have around 1.25 million subscribers, based on server statistics provided on TorStatus.net.

Creutz also noted that EA has begun to heavily promote the game, leading him to believe that this is in response to the stalling subscriber numbers.

"We believe that the apparent decline in subscribers is most likely due to a lack of 'end-game' content for the title, meaning that players who hit the level cap have few compelling options in terms of ongoing game play," he noted. "While the game got off to a good start, the relatively light amount of end-game content does appear to be taking a toll."

"We believe EA is attempting to address the end-game content issue, including a recent major game update, but momentum appears to have stalled and we believe it is prudent to adopt a more conservative forecast on subscribers at this time."

I guess we'll know for sure during EA's next investor conference call.